Jor-El, as we all know, discovered the Phantom Zone. However, this discovery came relatively late in his career. Prior to this discovery, the usual punishment for criminals on Krypton was to place them in a ship and put it in perpetual orbit of Krypton.

Roz-Em was one such criminal.

It's the nature of his crimes that's a little...off. Jor-El had a twin brother, Nim-El. Nim-El was in charge of Krypton's armory.

Roz-Em, spotting an opportunity to get some great guns, had himself surgically altered to appear as Nim-El. Unfortunately, he managed to go through all the trouble of plastic surgery without figuring out the usual time Nim-El would come back from his breaks at the armory. His plan is rather thus rather easily stopped. Jor-El, visiting his brother at the armory, simply helps Nim-El to just grab the guy.

Jor-El's the wrong guy to impersonate, though, because he's so highly placed in the government. He presumably gets rather more concerned about the security implications of having someone who looks like he and his brother walking around with criminal intent.

So, naturally, Roz-Em gets his ticket punched for the orbital prison. Up he goes where he'll never, ever cause trouble for the El boys again, right?

Right. But only because Krypton explodes. The only thing "perpetual" about space is that it's always in flux. All too easy to get your craft deflected from orbit by passing debris. And if Krypton exploded, well, that'd make it pretty hard for you to stay even in the same solar system.

So on Roz-Em goes, eventually drifting into a solar system that had a yellow sun. It wakes him up from his suspended animation, and he manages to piece together all that's happened, by using the Doppler effect to see into his own past. He traces Krypton's explosion and the lone egress of a tiny space vessel right at the moment of explosion.

Following its path, he goes to Earth at the time that Superboy is active. He manages to convince the young Kal-El and the Kents that he is Superman, the grown version of Kal-El. But, the Kent family works it out, and after some abuse of Clark with Kryptonite, Roz-Em is eventually dispatched.